A turbine is a power-generating machine in which a wheel is driven round by a stream of air, water, steam, or other fluid. Compounds indicate either the presence of a turbine or a device driven by one: turbocharger, a turbine powered by the engine's exhaust gases, so increasing its power; turbofan, a jet engine in which a turbine-driven fan provides additional thrust; turbojet, a jet engine in which the jet gases also operate a turbine-driven compressor for compressing the air drawn into the engine; turboprop, a jet engine in which a turbine is used to drive a propeller.